1. Field of the Invention
The present invention relates to a liquid crystal compound to be used for liquid crystal elements. More particularly, it relates to a new chiral substance which induces the twisted arrangement of liquid crystal.
2. Description of the Prior Art
There are two known operating modes of liquid crystal display devices. One is the twisted nematic mode for nematic liquid crystals and the other is the phase change mode for cholesteric liquid crystals. In these modes, the liquid crystal is incorporated with a chiral substance which induces the twisted arrangement of liquid crystal. On the other hand, there is a high-speed optical switch attracting attention which utilizes smectic liquid crystal, particularly smectic C* (SmC*) liquid crystal, characterized by its twisted arrangement and also utilizes its ferroelectricity. The SmC* liquid crystal is a chiral substance in itself, or the SmC* crystal is incorporated with a chiral substance.
The chiral substance that induces the twisted arrangement is of vital importance to liquid crystal display elements. The chiral substance used for liquid crystal display elements should have the optical rotary power; but it is not all that is required. What is required for the chiral substance is that it has the properties of being liquid crystal in itself or it does not greatly impair the performance of liquid crystal when it is added to a liquid crystal.
However, there has been only a few chiral substances that meet the above-mentioned requirements.